🚙 Bluetooth RC Car

Build a smartphone-controlled rover using an Arduino and Bluetooth module.

📋 Overview

The HC-05 module allows the Arduino to receive serial commands over Bluetooth from a smartphone app. You will parse these commands to control a dual-motor driver (L298N).

What you'll learn: Bluetooth serial communication, H-Bridge motor drivers, and basic command parsing.

Estimated time: 2-3 hours. Difficulty: ⭐⭐⭐ Intermediate.

🧩 Components Needed

Component	Specification	Qty	Notes
Arduino Uno R3	5V	1
HC-05 Bluetooth	Serial module	1
L298N Motor Driver	Dual H-Bridge	1
2WD Car Chassis	Includes 2 DC motors	1
Battery Pack	9V or 2S LiPo	1	For motors

📖 Step-by-Step Tutorial

Motor Driver Wiring

Connect Motors to OUT1/2 and OUT3/4. Connect 9V to L298N 12V input, and 5V output to Arduino 5V.

Arduino to Driver

Connect IN1, IN2, IN3, IN4 to digital pins 4, 5, 6, 7.

Bluetooth Wiring

Connect HC-05 TX to Arduino RX (Pin 0), and RX to Arduino TX (Pin 1) via a voltage divider (Bluetooth RX requires 3.3V).

Important Upload Step

Disconnect the Bluetooth TX/RX wires when uploading code, otherwise it interferes with USB communication.

💡

Always use a voltage divider (e.g. 1k and 2k resistors) between Arduino TX (5V) and HC-05 RX (3.3V) to prevent module damage over time.

💻 Code / Configuration

bt_car.ino

INO

// Bluetooth RC Car
int IN1 = 4, IN2 = 5, IN3 = 6, IN4 = 7;
char cmd;

void setup() {
  Serial.begin(9600); // Bluetooth default baud rate
  pinMode(IN1, OUTPUT); pinMode(IN2, OUTPUT);
  pinMode(IN3, OUTPUT); pinMode(IN4, OUTPUT);
}

void loop() {
  if (Serial.available() > 0) {
    cmd = Serial.read();
    if (cmd == 'F') { forward(); }
    else if (cmd == 'B') { backward(); }
    else if (cmd == 'S') { stopCar(); }
  }
}

void forward() {
  digitalWrite(IN1, HIGH); digitalWrite(IN2, LOW);
  digitalWrite(IN3, HIGH); digitalWrite(IN4, LOW);
}
void backward() {
  digitalWrite(IN1, LOW); digitalWrite(IN2, HIGH);

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